From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Subject: [PATCH 07/11] iio/adc: (max1363) Fix data conversion problems Date: Thu, 31 Jan 2013 13:43:04 -0800 Message-ID: <1359668588-13678-8-git-send-email-linux@roeck-us.net> References: <1359668588-13678-1-git-send-email-linux@roeck-us.net> Return-path: In-Reply-To: <1359668588-13678-1-git-send-email-linux-0h96xk9xTtrk1uMJSBkQmQ@public.gmane.org> Sender: linux-iio-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: linux-iio-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Jonathan Cameron Cc: devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, Naveen Krishna Chatradhi , Lars-Peter Clausen , Doug Anderson , Tomasz Figa , Grant Likely , Rob Herring , Guenter Roeck List-Id: devicetree@vger.kernel.org For chips with more than 8 bit ADC resolution, received data was always masked against 0xfff, ie with a 12 bit mask. This can result in bad data for chips with 10 bit resolution if those chips have higher bits set (seen with MAX1139). The receive buffer was defined as char array. This could result in unintentional sign extensions if the upper bit in a received byte was set. Since the chip is configured for unipolar mode, we never have to handle negative values, and sign extensions are never needed. Signed-off-by: Guenter Roeck --- drivers/iio/adc/max1363.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/iio/adc/max1363.c b/drivers/iio/adc/max1363.c index 2c773b4..fdc8be9 100644 --- a/drivers/iio/adc/max1363.c +++ b/drivers/iio/adc/max1363.c @@ -334,7 +334,7 @@ static int max1363_read_single_chan(struct iio_dev *indio_dev, { int ret = 0; s32 data; - char rxbuf[2]; + u8 rxbuf[2]; struct max1363_state *st = iio_priv(indio_dev); struct i2c_client *client = st->client; @@ -366,7 +366,8 @@ static int max1363_read_single_chan(struct iio_dev *indio_dev, ret = data; goto error_ret; } - data = (s32)(rxbuf[1]) | ((s32)(rxbuf[0] & 0x0F)) << 8; + data = (rxbuf[1] | rxbuf[0] << 8) & + ((1 << st->chip_info->bits) - 1); } else { /* Get reading */ data = i2c_master_recv(client, rxbuf, 1); -- 1.7.9.7